I am trying to figure out how to best use SA to create a GIS query.
In my application I am actually using ORM objects and mappers, but to
keep my question focused on clauses and python expressions, I am just
trying to test this out without the ORM first.
The SQL query I would like to generate is this:
select AsText(the_geom), *
from pt
where SetSRID('BOX3D(-95.0 28.5, -95.8 28.8)'::box3d,4326) && the_geom and
contains(SetSRID('BOX3D(-95.0 28.5, -95.8 28.8)'::box3d,4326), the_geom)
limit 100;
So far the best I have been able to come up with is this:
pt.select(
sa.and_(
pt.c.pos.op('&&')(func.SetSRID("'BOX3D(-95.0 28.5, -95.8
28.8)'::box3d",4326)),
func.contains(func.SetSRID("'BOX3D(-95 28.5, -95.8
28.8)'::box3d",4326), pt.c.pos)
)
)
Not the most readable way to represent it, but it seems to work. I
have a couple questions though.
- I reuse "func.SetSRID("'BOX3D(-95 28.5, -95.8 28.8)'::box3d",4326)"
twice. Is there a way to split this out into something I can just
reuse?
- Is there any way to write an extension "operator" or something that
could generate this for me? If I had my way, I would want the query
to look like this:
pt.select( smart_contains( ((-95 28.5, -95.8 28.82), 4326), pt.c.pos))
- Can anyone point out a better way I could construct this query? Is
there anything I am missing?
Thanks,
Allen
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